Several different amplifier circuit arrangements may be utilized to provide output signals. In one example, a class A amplifier circuit arrangement reproduces an entire input signal because an active element of the class A amplifier circuit arrangement, such as a transistor, is constantly in the active mode. However, class A amplifiers typically have a high power consumption because the active element does not stop conducting current.
In another example, a class B amplifier circuit arrangement reproduces half of the input signal since an active element of a class B amplifier circuit arrangement spends half of the time in active mode and the other half in cutoff. Class B amplifier circuit arrangements may include a push-pull configuration that has two active elements with one active element in active mode for half of an input waveform and the other active element in active mode for the other half of the input waveform. The properties of class B amplifier circuit arrangements may vary with load conditions and may suffer from harmonic distortion when the handoff from one element to another does not occur properly.
Class AB amplifier circuit arrangements are a mixture between class A amplifier circuit arrangements and class B amplifier circuit arrangements. Class AB amplifier circuit arrangements include two active elements that are in the active mode more than 50% of the time to decrease the amount of harmonic distortion that occurs during the handoff from one active element to another. Adjustment of output quiescent current in Class AB amplifier circuit arrangements may be problematic.
Some class AB amplifier circuit arrangements may utilize a stack of two diodes to adjust quiescent current. However, such arrangements do not typically operate well at low supply voltages because the stack of two diodes requires a relatively high supply voltage. Other class AB amplifier circuit arrangements may operate at low supply voltages, but may have increased current consumption. For example, class AB amplifier circuit arrangements may include current mirrors that generate a current internally and mirror the current to the output of the circuit arrangement. However, the current consumption of such class AB amplifier circuit arrangements is doubled. Still other class AB amplifier circuit arrangements may operate at low supply voltages and have low current consumption, but suffer from a poor power supply rejection ratio.